Photography



United States Patent 3,285,744 PHOTOGRAPHY Robert H. Sprague, Chagrin Falls, John A. Stewart, Parma, and James M. Lewis, Cleveland, Ohio, assignors to Horizons Incorporated, Cleveland, Ohio, a corporation of New Jersey No Drawing. Filed Apr. 4, 1963, Ser. No. 270,551

11 Claims. (CI. 96-90) to the processing of such compositions to yield a perma nent useful image.

(1) THE LEUCO COMPOUNDS The leuco compounds which may be utilized in accordance with the present invention comprise two recognized classes of dye forming colorless compounds, namely leuco triarylmethane dyes and a second class of leuco ,compounds, related to leuco xanthenes, leuco thioxanthenes and leuco acridenes.

The leuco bases of triarylmethane dyes which are suitable in the compositions about to be described more fully are those represented by the general formula wherein each R is selected from the group consisting of H, lower alkyl and 'aryl and the several Rs may be the same or different, and R is selected from the group consisting of H, aryl, alkyl and particularly wherein each of the R s is selected from the group consisting of H, alkyl and aryl.

Leuco dyes represented by the above formula which have been found suitable include:

leuco crystal violet leuco opal blue leuco malachite green leuco rosani-line leuco pararosaniline p,p,p"-trimethyl leuco opal blue p,p,p"-trichloro leuco opal blue p,p'-bis-tetramethyl-di-aminodiphenyl methane and other compounds ofa similar nature. 7

The other class of leuco compounds which are suitable in the composition about to be described more fully, are

generally similar to the leuco triarylmethane dyes except" that they are characterized by the presence of one or more 3,285,744 Patented Nov. 15, 1966 bridging hetero atoms and therefore are compounds which may be represented by the general formulas N Z\ N 31 0 11 \H and R1 R Z Rr i Rl wherein each R is selected from the group consisting of H, lower alkyl and aryl and may be the same or different and R is selected from the group consisting of H, alkyl and aryl, including particularly and wherein Z represents a member selected from the group consisting of O, S, Se and NH.

As indicated, the preferred leuco compounds of this class are substituted in the 3,6-positions and include 3,6-bis (dimethylamino) -9- p-dimethylaminophenyl) Xanthene 3 6-bis diethylamino) -9- (p-dimethylaminophenyl) xanthene 3,6-bis (diethylamino) -9- ('p-diethylaminophenyl) xanthene 3 ,6-bis dimethylamino -9- p-dimethylaminophenyl) thioxanthene. v

(2) THE ACTIVATORS A diverse group of colorless non-toxic sulfur-containing organic compounds have been found useful in the present invention. These fall into a number of classes as follows:

(1) Mercapto compounds of the general formula RSH wherein the mer-capto group is attached to a carbon atom in a heterocyclic nucleus of the type commonly used in cyanine dye chemistry, for example 2-quinoline B-naphthothiazole 4-quino1ine oxazole Z-pyridine benzoxazole 4-pyridine fl-naphthoxazole imidazole selenazole ben'zimidazole benzoselenazole thiazole thiazoline benzothiazole and the like.

(2) Disulfides of the general formula RSSR wherein R has the same meaning as in 1 above.

wherein R'f is selected from the group consisting of H,

lower alkyl and aryl.

(4) Sulfides wherein the sulfide sulfur is attached to a carbon atom in a'heterocyclic ring wherein the same gcarbon atom is attached to two non-carbon atoms e.g.

as in rhodanine or tetrazole.

(5) Thioureas. (6) Acyclic thioacetanilides.

(3) EVALUATION PROCEDURE The data reported in the tables which follow is the Command (USAF), and is defined as the reciprocal 'of the exposure in meter candle seconds which is required to produce a double difiuse reflection density of 0.2 density units above base plus fog. As in the more conventional ASA system used to rate silver halide films, the

result of tests establishing the effect of visible light on 5 higher th LES, number th faster the film is. mixtures of various activator compounds with the indi- Results of exposure tests With compositions consisting cated leuco bases. In general one of three procedures of equal weights of 3,6-bis(dimethylamino)-9-(p-dimethwas followed. ylaminophenyl)xanthene and various activators, dis- In the first two, a mixture is prepared conslstmg o solved in a mixture consisting of 2 cc. of acetone and equal parts by volume of acetone and a 10% solution of 10 2 cc. of a 10% solution of polystyrene in benzene, coated, polystyrene in benzene, 2 cc. of each belng used in most .0015 inch wet thickness on Mylar film, dried, exposed instances. Then the indicated weights of the leuco comfor 5 minutes to 1 General Electric No. 2 Reflector Photopound and of the activator were dissolved in the mixture. flood lamp at a distance of 12 inches from lamp to photo- The resulting composition formed from originally colorsensitive material through a silver step tablet and solvent less materials had a Cloudy 0r Y aPPeaIaflCe Or a fixed by at least two rinses in amixture of 1 part acetone faint pinkish color in most lnstances. The composition and 4'parts petroleum ether.

Table I w 1 ht N b Density e um 81' N o. Activator in n ig. of steps Gross Base plus Net Fog 2-mercaptobenzoxazole. I 50 21 2.55 0.09 2.46 100 21 2.85 0.05 2.80 2mercapt0benzoth1azole 50 21 2 .14 0 .09 2 .05 100 21 2.3 0.07 2.81 2-mercaptobenzimidazole 100 10 0 .22 0.10 0.15 Z-mereapto-fi-mtrobenzothiazole 50 21 1 .30 0.09 1 .21 2-metcaptothiazoline 100 10 1 .75 0.05 1 .70 2-mercapto-4-phenylthiazole. 100 21 1 .84 0.30 1 .54 2.-mereapto-1-methylimidazole- 100 11 1 .21 0.05 1 .16 1-phenyl-5-mercapt0tetrazole 100 21 3 .0+ 0 .35 2 .65+ 2-mercapto-4,6,6-trnnethylthiazine 100 13 1 .82 0.05 1 .77 2-mercapto-4-phenylthiazole 100 21 1.84 0.30 1.54 2-mercaptoquinoline 100 12 1.17 0 .06 1.11 2-mereapto-fi-naphthothiazole 100 21 1 .90 0.13 1 .77 2-r nercapto-pyr1dine 100 8 0 .62 0.04 0 .58 14 Bis(d imethylthiocarbamyl)dlsulfide 100 11 0.76 0.09 0.67 15 2,2-d1th10b1s(benzothiazole) 40 15 0.49 0.06 0.43 B s(3-phenyl-2-1ndolyl) disulfide. 100 13 0 .62 0 .06 0 .56 Bis(4-ph enylth1az0le) -2-disn1fide 100 13 1.60 0.10 1.50 Rhnrlanme 100 21 2.29 0.11 2.18 Rhodanine (heat fixed) 100 21 3 .00 0.89 2.11 19 2,4-th1azol1d1ned one (heat fixed) 75 15 2.80 0.17 2.63 20 4-nrercaptopyr1dlne (heat fixed). 100 16 0.55 0.07 0.48 21 Thioacetanllide (heat fixed) 75 17 1.80 0.35 1.45 22 a-Mercaptoacetanilide (heat fixed) 50 14 1.59 0.15 1 .44 23 Thlocarbanilide (heat fixed) 50 14 2.38 0.23 2.15

was coated by means of a Bird applicator on 500-D Mylar in a coating having a 0.0015 inch wet thickness and the coating was permitted to dry in air. Thereafter the composition was exposed either to a hotoflood lamp through a step tablet or on an Eastman Kodak Sensitometer with a suitable filter.

When the composition was exposed to a General Electric 500 watt RFL-2 Photoflood lamp exposure was through a #2 silver step wedge for a 5-minute interval at a distance of 12 inches from lamp to test materials. The density and number of steps visible in the image were red, after fixing the image by solvent wash or by heat.

When the composition was exposed on an Eastman Kodak No. 101 sensitometer the light was converted by the use of a 78AA filter, to equal mean noon-day light. The resulting image was fixed by a solvent wash or by exposure to heat. Thereafter the density of the image was red and the LES. was computed as described above.

In a third procedure, the polystyrene was omitted from the compositions and instead a mixture of benzene and acetone was used as the solvent for the indicated amounts of the leuco compound and the activator. The solution was poured onto filter paper and the photosensitive material was then expose-d through an Eastman No. 2 step tablet to one General Electric Reflector Photoflood lamp for seconds at a distance of 12 inches from the lamp to the sensitive material. The densities of the resulting step wedge were read on an Eastman No. 1 color densi-. tometer through the green filter.

L.E.S. (abbrevation for light exposure speed) refers to a speed rating system developed at the Wright Air Development Division of Air Research and Development in Table II.

The same compositions as those in Table I were exposed using an Eastman No. 101 sensitometer with the light converted by the use of a 78AA Eastman filter to equal mean noon-day light and the exposed material was stabilized by two or more successive rinses in a mixture of 1 part acetone and 4 parts petroleum ether. The stabilized material was reexposed 4 minutes to the RFL- 2 with no darkening. The densities'in the resulting step Wedges were read with an Eastman No. 1 color densitometer using the green filter, the results were as reported Table II Density Number No. Exp. Min. 01 steps L.E.S.

Gross Base plus Fog 60 6 0. 25" 0. 09 Too slow 60 11 0. 43 0. 10 2.4)(10- 2 10 0.58 015 1x10 60 6 0. 55 0. 08 1.8X10- 2 12 0.86 0. 26 1.4X10- 60 11 0.72 O. 08 4.3X10- 2 I 9 0.58 0.15 1.0X10- 60 11 0. 44 0. 09 2.3X10 60 8 0.42 0.14 1.1)(10- 60 4 0.32 0. 08 1.7X10- 60 6 0. 53 0. 10 1.9X10

60 6 0.47 0. 09 2.5 1O 2 9 0.38 0. 13 4.2X10-u Table II-Continued 6 The coatings were exposed under an Eastman No. 2 Step Tablet for 5 minutes to one General Electric No.

Density 2 Reflector Photoflood lamp at a distance of 12 inches Number No. Exp. Mm orsteps L'Efi from the lamp to the photosensitive material.

Gross Base plus 5 Exposures were also made, uslng an Eastman No. 101 Fog sensitometer with the light converted by the use of a 60 13 1 O 17 6x104 78AA Eastman filter to equal mean noonday light. 60 13 1 1 1 4 The exposed material was stabilized by two or more 28 8-1 2 successive rinses in a mixture of 1 part acetone and 4 a0 4 0140 012a 211x10 10 parts petroleum ether. The stabilized material was reexposed 5 minutes to the RFL 2, with no darkening. The Utilizing the filter paper procedure described above, densities in the resulting step wedges were read with an with a solvent mixture consisting of 4 cc. of acetone and Eastman No. 1 color densitometer, using the green filter.

Table IV Exposed to N o. 101 Exposed to RFL-2 Leuco Weight Exp. Number Densities Densities Compound in mg. Min. of Steps Gross Base-I-Fog L.E.S. Gross Base+F0g (1 100 00 14 1.s 10 100 5 21 2.81 0.09 100 00 15 2. 8X10- 100 5 21 0.72 0.07 100 90 5 9.4 10 100 5 11 1.47 0.06 100 00 6 1.5 10 100 5 16 2.20 0.05 1s 0.5x1lH 50 5 21 2.14 0. 09 100 2 18 1.2x10- 100 5 21 2.88 0.07

Leuco Compounds:

(1) 3,6-bis(diethy1amino)-9-(p-dimethylaminophenyl)xanthene. (2) Leuco Opal Blue (tri-(p-anilino)-triphenyln1ethane). (3) Tri-(p-diethylaminophenyl)methane. (4) Leuco Crystal Violet. (5) 3,6-bis dimethylamino-Q-(p-dimethylaminophenyi)xanthene.

4 cc. of benzene and containing 100 mg. of 3,6-bis(di- FIXING methylamino) 9 (p dimethylaminophenyl)xanthene as the leuco dye base and 100 mg. of the activator or sensitizer or in instances where the 100 mg. of activator would not dissolve, a saturated solution of the activator was used.

, exposed material is subjected to mild heat (125 C.) for Table III Densities Weight Solvent, N o. N 0. Activator in mg. cc. Steps Max Base Net. Den +Fog Den.

1 None 0 8 3 1.05 0.75 0.30 2 2,2-dithio-bls(benz0- 100 8 8 2. 51 1. 25 1. 26

thiazole 3 2,3-quinoxalinedithlon. "S 8 11 2. 08 0.80 1. 28 4".-- Bis(2-quinolyl)disulfide 100 8 15 1.80 0.73 1. 07 5 Bis (3-phenyl-2-indoly1) 100 8 16 1. 90 0. 70 1. 20

disulfide. 6 Z-mercapto-B-naptho- 100 8 21 3+ 0.80 2. 2

thiazole. 7 Bis(B-naphthothiazole)- 100 8 14 1.65 0. 1. 00

Z-dlsulfide. 8. 2-mercaptobenzothiazole 100 8 10 3+ 2. 05 0. 95 9. 2-quinoline isothiou- S 8 5 1. 52 1. 00 0. 52

ronium chloride.

Saturated solution.

\ Z-mercaptobenzothiazo-le were dissolved in the mixture.

The resulting solution was coated at a wet thickness of 0.0015-inch with a Bird applicator bar on unsubbed 300-D Mylar. The coatings were air-dried for approximately 15 minutes before exposure.

about 4 minutes. The method of stabilization selected in any specific instance will depend to some extent upon the materials being used and it is to be noted that many of the slower compositions may be preferable to some of the faster compositions because some of the latter are less susceptible to heat or dry fixing than some of the former.

While not wishing to be bound by any specific theory as to the manner in which the exposure to visible light to an intimate mixture comprising two or more originally colorless compounds produces a colored image, it is believed that the final colored image which forms in the light struck areas is always the dye which forms as a result of oxidation of the leuco base. Furthermore it appears that when the photosensitive mixture is prepared, on mixing the compounds which are colorless, a weakly tinted mixture is formed.

It is also considered possible that the real active ingredient in the mixture is that very minute amount of an oxidized product which results when the leuco base is exposed to oxygen e.g. in the ordinary atmosphere.

Whatever the true mechanism each of the activators listed above, or mixtures of the same, bring about oxidation of the leuco compound upon exposure to a suitable dose of visible light and as a result form a direct visible print-out image in the light struck areas.

PROPORTI OLNS The relative proportions of the leuco dye bases and the activators forthe same may be varied considerably from the 1:1 weight proportions given by way of illustration in the examples and are preferably within the range between to 1 and 1 to 10 parts by weight.

As with other photosensitive compositions if not used at the time they are prepared the compositions of the present invention should be stored in cool dark relatively dry surroundings.

Having now described the invention in accordance with the patent statues it is not intended that it be limited except as may be required by the appended claims.

We claim:

1. A composition which prints out a visible image directly as a result of exposure to visible light said composition consisting essentially of an intimate mixture of (1) at least one leuco compound selected from the group consisting of leuco compounds represented by one of the following general formulas wherein each R is selected from the group consisting of H, lower alkyl and aryl and not all of the Rs need be the same;

R R N /Z\ N/ R/ \'R i 122 H wherein each R has the samemeaning as indicated above and R is selected from the group consisting of H, lower alkyl and aryl;

organic compound selected from the group consisting of (a) mercapto compounds represented by the formula R'-SH wherein R is a heterocyclic nucleus of the type commonly used in cyanine dye chemistry;

(b) disulfides represented by the general formula R'ASR wherein each R has the same meaning as in (a);

(c) disulfides of the general formula wherein R represents H, alkyl and aryl; (d) thiourea compounds; (e) acyclic thioacetanilides;

said compounds being present in said mixture in proportions ranging between 10:1 and 1: 10 relative to each other, by weight.

2. The composition of claim 1 wherein the leuco compound is a leuco base of a triphenylmethane dye.

3. The com-position of claim 1 wherein the sulfur containing compoundis a 2-mercapto heterocyclic compound.

4. The composition of claim 3 wherein the sulfur containing compound is Z-mercaptobenzothiazole.

5. The composition of claim 1 wherein the mixture consists of 3,6-bis(dimethylamino)-9-(p-dimethylaminophenyl)xanthene and a heterocyclic mercaptan.

6. A dry film consisting of the compositions of claim 1 dispersed in a thin layer on an inert support.

7. The film of claim 2 wherein the support is a film forming plastic.

8. The film of claim 2 wherein the binder is a cellulose compound selected from the group consisting of cellulose and cellulose derivatives.

9. The film of claim 2 wherein the support is transparent.

10. The process of producing a direct print-out image from originally colorless compounds which comprises preparing the composition of claim 1 in the form of a thin layer, exposing said layer to visible light and fixing the image which prints out directly as a result of said exposure.

11. The composition of claim 1 wherein the leuco compound is a leucoxanthene.

References Cited by the Examiner UNITED STATES PATENTS 1,850,162 3/1932 Wendt et al 9648 1,871,830 8/1932 Wendt et al. 9648 1,918,623 7/1933 Wendt 9690 2,082,178 6/1937 Ochwat et al. 9690 2,281,895 5/1942 Poser et al 9689 X 3,042,515 7/ 1962 Wainer 9690 X 3,042,516 7/1962 Wainer 9690- 3,055,758 9/1962 McDonald 9648 3,100,703 8/1963 Sprague et al 9690 3,104,973 9/1963 Sprague et al. 9689 3,113,024 12/1963 Sprague et al 9690 X OTHER REFERENCES Menzies, D. W.: Photo-Sensitivity of Thiazine Leucobases, Nature, 191, 505-6 (July 29, 1961).

Sprague et al.: Investigation of Photopolymerization Processes, ASD Tech. Report 61-82, May 15, 1961 (AD- 258412-L), pages 1-18 are of interest.

NORMAN G. TORCHIN, Primary Examiner.

A. L. LIBERMAN, D. PRICE, Assistant Examiners 

1. A COMPOSITION WHICH PRINTS OUT A VISIBLE IMAGE DIRECTLY AS A RESULT OF EXPOSURE TO VISIBLE LIGHT-SAID COMPOSITION CONSISTING ESSENTIALLY OF AN INTIMATE MIXTURE OF (1) AT LEAST ONE LEUCO COMPOUND SELECTED FROM THE GROUP CONSISTING OF LEUCO COMPOUNDS REPRESENTED BY ONE OF THE FOLLOWING GENERAL FORMULAS 